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Installing AC/DC Combination
Alarms as Replacements with
Existing Interconnected Firex Alarms
Model FADCQ combination alarms are designed
to be used as replacement units for all Firex AC
and AC/DC smoke alarms with a low voltage
interconnect line. These models include G, GC,
H, AD, ADC, and FADC. All models listed use a
3-wire interconnect system. To interconnect with
other models, please call our free technical
support line at (800) 445-8299.
IMPORTANT! READ BEFORE INSTALLING
THIS SMOKE AND CO ALARM WITH EXISTING
INTERCONNECTED FIREX ALARMS
In residential homes, there are two ways smoke
and CO alarms are hardwire installed and inter-
connected. One uses 4 wires, the other uses 3
wires.
The Model FADCQ smoke and CO alarm can be
used with both 4 and 3 wire systems.
1. Identify whether the installed system uses 3 or
4 wires to interconnect.
2. If a 4-wire system is installed, change the sys-
tem to a 3-wire by connecting the independant
interconnect wires (yellow and blue) at any
point in the system.
3. Smoke alarms generally don’t require any
changes (other than replacement every ten
years).
4. Replace older CO alarms on the new 3-wire
system with COQ-8 CO alarms or FADCQ com-
bination alarms. These alarms can discriminate
between signals coming from a smoke alarm
and signals coming from a CO alarm. Older
model CO models converted to 3-wire cannot.
So when any alarm is triggered, all the older
CO alarms will sound, creating confusion about
which danger is actually present.
To Install Combination Unit as a Replacement:
1. Turn off AC power at circuit breaker or main
fuse box.
2. Remove old alarm from mounting bracket.
3. Disconnect wire connector from back of unit.
4. Remove wire nuts and connect new wire con-
nector to household wiring. Be certain not to
cross the wiring.
5. Connect wire connector to back of combina-
tion alarm.
6. If mounting bracket is the same, reattach
combo alarm to mounting bracket. Feed wiring
back through hole in mounting surface.
7. Turn on power at main fuse box or circuit
breaker.
8. Test combination alarm. See “TESTING THE
COMBINATION ALARM.”
9. Activate the battery. Remove arrow tab and
close battery door. The combination alarm will
beep briefly and the RED light will flash as
door is closed.
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